Generally, photolithography comprises deposition of a light-sensitive resist or photoresist material on a substrate, and a portion of the light-sensitive resist material is exposed to a source of radiation through a mask. As a result of exposure, the photoresist may become either more or less soluble in a developer solution. That is, the solubility of the exposed regions of the photoresist may be switched (i.e., solubility switching) and the soluble portions of the photoresist are removed during development.
In recent years, molecular glass photoresists have received significant attention as potential replacements for polymer-based photoresists in sub-65 nanometer (nm) advanced photolithography. Among the perceived advantages of molecular resists over polymers are at least: (1) they can be repeatedly synthesized with precise molecular weight, compositional, and stereochemical control, and (2) their much smaller molecular size and consistent molecular composition should improve dissolution inhomogeneity which can reduce line-edge-roughness (LER). Molecular resists have been shown, both in simulation and experiment, to provide improvements in LER compared to polymer resists.
Although molecular glass materials may offer many potential advantages over polymeric CARs, there are still many things that are unknown about this class of materials that could potentially cause problems. Removal and subsequent volatilization of protecting groups in positive tone molecular resists can cause a loss of up to approximately 50% of the mass of the resist, possibly leading to a loss of pattern quality. The small sizes of molecular resist compounds, and often correspondingly low glass transition temperatures, can also lead to problems, such as more significant photo-acid diffusion and reduced mechanical strength and integrity.
Accordingly, there is a need for improved molecular glass resists. It is to the provision and characterization of such molecular glass resists that the various embodiments of the present invention are directed.